diff --git a/DDCore/include/DDSegmentation/CylindricalGridPhiZ.h b/DDCore/include/DDSegmentation/CylindricalGridPhiZ.h
index 54a836934..d81ce3702 100644
--- a/DDCore/include/DDSegmentation/CylindricalGridPhiZ.h
+++ b/DDCore/include/DDSegmentation/CylindricalGridPhiZ.h
@@ -104,6 +104,9 @@ namespace dd4hep {
       */
       virtual std::vector<double> cellDimensions(const CellID& cellID) const;
 
+      /// Set the underlying decoder (setting, inter alia, whether phi isSigned)
+      virtual void setDecoder(const BitFieldCoder* decoder);
+
     protected:
       /// the grid size in phi
       double _gridSizePhi;
@@ -119,7 +122,8 @@ namespace dd4hep {
       std::string _phiId;
       /// the field name used for Z
       std::string _zId;
-      /// encoding field used for the module
+      /// the isSigned attribute of the bitfield used for phi
+      bool _phiIsSigned;
     };
 
   } /* namespace DDSegmentation */
diff --git a/DDCore/include/DDSegmentation/PolarGridRPhi2.h b/DDCore/include/DDSegmentation/PolarGridRPhi2.h
index 0e859027c..57d53fa33 100644
--- a/DDCore/include/DDSegmentation/PolarGridRPhi2.h
+++ b/DDCore/include/DDSegmentation/PolarGridRPhi2.h
@@ -140,6 +140,9 @@ namespace dd4hep {
       */
       virtual std::vector<double> cellDimensions(const CellID& cellID) const;
 
+      /// Set the underlying decoder (setting, inter alia, whether Phi isSigned)
+      virtual void setDecoder(const BitFieldCoder* decoder);
+
     protected:
       /// the grid boundaries in R
       std::vector<double> _gridRValues;
@@ -153,6 +156,8 @@ namespace dd4hep {
       std::string _rId;
       /// the field name used for Phi
       std::string _phiId;
+      /// the isSigned attribute of the bitfield used for Phi
+      bool _phiIsSigned;
     };
 
   } /* namespace DDSegmentation */
diff --git a/DDCore/src/segmentations/CylindricalGridPhiZ.cpp b/DDCore/src/segmentations/CylindricalGridPhiZ.cpp
index 36e731ff3..c17a45c0f 100644
--- a/DDCore/src/segmentations/CylindricalGridPhiZ.cpp
+++ b/DDCore/src/segmentations/CylindricalGridPhiZ.cpp
@@ -62,6 +62,13 @@ CylindricalGridPhiZ::~CylindricalGridPhiZ() {
 
 }
 
+/// Set the underlying decoder and assign isPrimed attribute to phi identifier
+void CylindricalGridPhiZ::setDecoder(const BitFieldCoder* newDecoder) {
+  this->Segmentation::setDecoder(newDecoder);
+  const BitFieldElement* m_phi = &((*_decoder)[_phiId]);
+  _phiIsSigned = m_phi->isSigned();
+}
+
 /// determine the position based on the cell ID
 Vector3D CylindricalGridPhiZ::position(const CellID& cID) const {
 	vector<double> localPosition(3);
@@ -80,7 +87,7 @@ Vector3D CylindricalGridPhiZ::position(const CellID& cID) const {
   CellID CylindricalGridPhiZ::cellID(const Vector3D& localPosition, const Vector3D& /* globalPosition */, const VolumeID& vID) const {
 	double phi = atan2(localPosition.Y,localPosition.X);
 	double Z = localPosition.Z;
-	if ( phi < _offsetPhi) {
+	if (!_phiIsSigned && phi < _offsetPhi) {
 	  phi += 2*M_PI;
 	}
         CellID cID = vID ;
diff --git a/DDCore/src/segmentations/PolarGridRPhi2.cpp b/DDCore/src/segmentations/PolarGridRPhi2.cpp
index b294315ae..744ce6b7e 100644
--- a/DDCore/src/segmentations/PolarGridRPhi2.cpp
+++ b/DDCore/src/segmentations/PolarGridRPhi2.cpp
@@ -55,6 +55,13 @@ PolarGridRPhi2::PolarGridRPhi2(const BitFieldCoder* decode) :
 /// destructor
 PolarGridRPhi2::~PolarGridRPhi2() {
 
+}
+
+  /// Set the underlying decoder and assign isPrimed attribute to Phi identifier
+void PolarGridRPhi2::setDecoder(const BitFieldCoder* newDecoder) {
+  this->Segmentation::setDecoder(newDecoder);
+  const BitFieldElement* m_phi = &((*_decoder)[_phiId]);
+  _phiIsSigned = m_phi->isSigned();
 }
 
 /// determine the position based on the cell ID
@@ -64,10 +71,6 @@ Vector3D PolarGridRPhi2::position(const CellID& cID) const {
 	double R = binToPosition(rBin, _gridRValues, _offsetR);
 	double phi = binToPosition(_decoder->get(cID,_phiId), _gridPhiValues[rBin], _offsetPhi+_gridPhiValues[rBin]*0.5);
 
-	if ( phi < _offsetPhi) {
-	  phi += 2*M_PI;
-	}
-	
 	cellPosition.X = R * cos(phi);
 	cellPosition.Y = R * sin(phi);
  	
@@ -85,7 +88,7 @@ Vector3D PolarGridRPhi2::position(const CellID& cID) const {
 	CellID cID = vID ;
 	_decoder->set(cID,_rId, rBin);
 
-	if ( phi < _offsetPhi) {
+	if (!_phiIsSigned && phi < _offsetPhi) {
 	  phi += 2*M_PI;
 	}
 	const int pBin = positionToBin(phi, _gridPhiValues[rBin], _offsetPhi+_gridPhiValues[rBin]*0.5);